The present invention relates to a steel substrate having a zinc diffused nickel alloy coating thereon and to a method for forming same.
Steel products are subject to damage from atmospheric corrosion and must be protected. This is often accomplished by applying a protective coating such as an organic film (paint) or a metallic coating (electroplate). Steel is also subject to heat oxidation at high temperatures and, if it is to be subjected to this environment, it must be protected via an appropriate coating. Electroplated or sprayed metal coatings or metallized paints are often used to provide resistance to high heat environments, such as those found in gas turbine engines. Problems arise when both heat and atmospheric corrosion protection are needed. Coatings resistant to high heat generally do not impart effective atmospheric corrosion protection, while typical coatings capable of preventing atmospheric corrosion offer little thermal protection beyond 420xc2x0 C. (approximately 790xc2x0 F.)
Accordingly, it is an object of the present invention to provide a coating which provides both heat and atmospheric corrosion protection.
It is yet another object of the present invention to provide a method for forming the above coating.
The foregoing objects are attained by the coating and the method of the present invention.
In accordance with a first aspect of the present invention, a method for forming a corrosion and heat protective coating on a substrate is provided. The method broadly comprises the steps of forming a nickel base coating layer on the substrate, applying a layer of zinc over the nickel alloy coating layer, and diffusing the zinc into the nickel alloy coating layer. If desired, the coated substrate may be immersed in a phosphated trivalent chromium conversion solution either before or after the diffusing step.
In accordance with a second aspect of the present invention, a steel substrate having at least one surface and a zinc diffused nickel alloy coating on the at least one surface is provided.
Other details of the method and the coatings of the present invention, as well as other-objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.